Significant concentrations (Details Textual) - Concentration Risk Benchmark [Domain]	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Unusual Risk or Uncertainty [Line Items]
Minimum Percentage Of Profit Allocated To Foreign Investment	10.00%
Registered Capital Percentage	50.00%
Ten Largest Customers [Member]
Unusual Risk or Uncertainty [Line Items]
Concentration Risk, Percentage	70.40%	68.70%
Customer One [Member]
Unusual Risk or Uncertainty [Line Items]
Accounts Receivable Trade Percentage	5.80%	4.90%
Concentration Risk, Percentage	12.80%	11.60%
Customer Two [Member]
Unusual Risk or Uncertainty [Line Items]
Accounts Receivable Trade Percentage	11.40%	12.30%